An X-ray computed tomography apparatus includes an X-ray detector which detects X-rays. The X-ray detector includes a plurality of detector cells which detect X-rays and a plurality of DAS (Data Acquisition System) elements which process electrical signals from the respective detector cells. More specifically, the DAS elements read out electrical signals from the detector cells, integrate the readout electrical signals, and convert the integral signal into digital data.
A high-resolution detector has also been developed, which has an array of a plurality of detector cells, each having a size smaller than a standard size, to acquire data with a high resolution. As schemes of reading out electrical signals from detector cells, a simultaneous readout scheme and a sequential readout scheme are known. In the simultaneous readout scheme, a plurality of detector cells are connected one-to-one to a plurality of DAS elements. The simultaneous readout scheme can achieve simultaneity in terms of integration time between detector cells and high-speed readout of electrical signals, but is technically difficult to be implemented in a high-resolution detector because of high-density signal wiring lines between detector cells and DAS elements. In addition, in the simultaneous readout scheme, although detector cells are directly connected to DAS elements via through electrodes, the contact area of each through electrode to a corresponding detector cell occupies a large part of the cell area. This makes it difficult to reduce the cell size. In the sequential readout scheme, a plurality of detector cells are connected to DAS elements via common signal wiring lines. For this reason, the sequential readout scheme allows a reduction in cell size more easily than the simultaneous readout scheme. In addition, in the sequential readout scheme, because of the above wiring scheme, the density of signal wiring lines between detector cells and DAS elements does not become high even when using a high-resolution detector, but simultaneity in terms of integration time between the detector cells collapses.